There are basically two different types of external aquarium power filter, one, which is the hang-on type, and another is the canister filter. What differentiates between both types depend on the filtration capacity to treat higher gallons of water per hour and basically the canister type is more powerful compared to hang-on filter. External filter is a preferred option among aquarium fish hobbyist and it’s a popular choice especially for large community tanks. Since it is placed outside of the aquarium, maintenance work can be simplified and servicing can be performed with ease without worry of contaminating the water when you take out the filter media.
Perhaps the only thing you have to be careful when using external power filter is to watch out whether strong output of water may cause certain small-sized fish like neon tetra, hatchet fish or guppy to lose balance in the water especially for mini aquariums. Therefore make sure that you check with the pet store salesperson before making your purchase so that you don’t oversize your external filter to be too big, above the maximum filtration capacity needed. Other than that, steps must also be taken to ensure that these fish do not get sucked in to the tube due to the high inflow of aquarium water. Most of the time, the filter purchase comes with it’s own inlet tube block or strainer which must be fixed according to the original buildup and not discard the parts aside as what most people always do.
Today, there are quite a number of popular brands like Fluval, Eheim, Hagen, just to name a few. They all vary in filtration capacity made for different aquarium tank size while some are even sold together with filter media so that the aquarium owner can straight plug it in and run. Some options also include spray bar at the output line so that this will help in water distribution and also contribute towards higher aeration. Based on my experience, external power filter is definitely the best option for your aquarium fish tank.